There are 3 species of Witch-Hazel native to North America that flower late winter that might have possibilities. I love Witch-hazel for the landscape and feel that they are under utilized. I've considered trying to use them in bonsai but have not yet.

The only native I can think of is witch hazel. I've seen photos of bonsai specimens, but have never seen on in person. Redbud is definitely a spring blooming tree...fairly early but definitely spring.

If you can stretch your definition slightly to include some non-native but commonly found plants, you could include camellia...some of which bloom in the fall and winter. I have a young camellia sasanqua 'yuletide' bonsai that blooms in November/December.

The native question always bothers me. While I can understand it's importance in the landscape or in creating a mood, do most people who talk natives really know one from another? A local sensei recommends natives for accents, but then displays an invasive weed from Europe. I wouldn't want to introduce that to my garden. Finding a true native that blooms in fall or "winter" would be easier in a climate zone above 8, although the blooming of the plant may signal the start of that areas early spring. The witch hazel would be a good native for readers on the US east coast. Why would a SW coast person think of that as native? Wouldn't a look into Mexico's flora be more realistic ? Lucky the person who can call the Camellia native. Or perhaps Daphane bholua?

I suppose "native to where?" is a good question. I love our natives (to North America) and try to use them as much as possible. The Native Americans took plants with them all over this continent and we have a few species of Yucca and Opuntia (prickly pear cactus) that occur in Tennessee. One good one is called Chickasaw Plum. It's Prunus angustifolia. I'd call it a good native substitute for Prunus mume as it has small white flowers and craggy bark. It too was likely moved around by the locals as it occurs from central Florida up into New England from what I've read.

Deciduous winter flowering species are my favorite and I'm on the hunt for more. Hamamalis vernalis, our native Witchhazel is a nice one. Amelanchair arborea, our native Service Berry is another as RockM said. As for others native to this side of the continent, there are a few that I haven't seen used for bonsai much. I'm looking into the matter now. I believe there are a few species of Hawthorne that flower in winter.

As for kusamono, this is another matter I've been looking into. Visit native plant nurseries throughout the year as I do and you can see some interesting stuff; the flowers on many are short-lived for sure. I've been looking into some native mustards and other cedar glade plants that grow on granite out-croppings.

Sorry Native to the U.S. There are are few reasons why i'm interested in Natives, mainly because the possibility of collecting a specimen. I am also searching for Native's that would flower during late winter. Something similar to Ume would be great, there's one in CA called Prunus Subcordata that I have, but it's not that impressive. Hope to have a better one in the future.